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High‐Performance Blue Quantum Dot Light‐Emitting Diodes with Balanced Charge Injection
Author(s) -
Cheng Tai,
Wang Fuzhi,
Sun Wenda,
Wang Zhibin,
Zhang Jin,
You Baogui,
Li Yang,
Hayat Tasawar,
Alsaed Ahmed,
Tan Zhan'ao
Publication year - 2019
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.201800794
Subject(s) - quantum dot , materials science , optoelectronics , light emitting diode , annealing (glass) , diode , luminance , cathode , electron , optics , chemistry , physics , composite material , quantum mechanics
The balance of hole–electron injection is always a vital factor for the luminance, efficiency and working lifetime of quantum‐dot light‐emitting diodes (QLEDs), especially blue QLEDs. However, currently most approaches proposed to solve this issue involve tedious optimization of device architecture or material composition. Here, high‐performance blue QLEDs are reported based on CdZnS/ZnS quantum‐dot (QDs) by utilizing ZnO nanoparticles (NPs) and Al:Al 2 O 3 as electron‐transporting layer (ETL) and cathode materials, respectively. The effect of post‐annealing temperature on the trap state density in ZnO NPs and the related mechanisms are investigated through optical and photoelectron spectroscopies. The method of controlling ZnO NPs annealing temperature leads to controllable electron‐mobility of ETL, which ultimately optimizes the balance of charge injection. Together with partially oxidized Al cathode (Al:Al 2 O 3 ), high‐performance blue QLEDs are fabricated with luminance and external quantum efficiency (EQE) up to 27 753 cd m −2 and 8.92%. As far as is known, the peak luminance achieved is the record of deep blue QLEDs. This simple method for regulating charge injection balance via annealing temperature requires no modification of device architecture, making it applicable for a variety of QLEDs structures.